University of Massachusetts Amherst

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Departmental Seminar: Cassie-Baxter versus Wenzel: What’s the Role of Microgeometry in Friction Reduction?


Monday, November 17, 2014 - 4:00pm


Carlos Hidrovo, Department of Mechanical Engineering, Northeastern University


Kellogg Room, ELab II


Surface microtexturing can lead to a superhydrophobic Cassie-Baxter state characterized by the presence of air pockets within the roughness. It is widely believed that these air pockets act as effective “shear free” (or at least shear reducing) regions that lead to lower global friction. In this talk we will explore the effects of pressure on the degree of microtexturing wetting and corresponding friction reduction characteristics in microchannel flow. It will be shown that friction reduction is for the most part insensitive to the degree of microtexturing wetting. Furthermore, under certain conditions a fully wetted Wenzel state can lead to lower friction characteristics than those of the un-wetted Cassie-Baxter state. Hydrodynamics and physicochemical interfacial phenomena provide insight into these behaviors. These findings can have major implications in the way we think about how these surfaces achieve friction reduction and in the optimization of microgeometries for specific applications.